The Army Expects Its New Rifle to Be of a Different Caliber

When the Army ordered its now standard M4 carbine in 1993 from firearms maker Colt, it saw the rifle as a lighter, more agile alternative to the Vietnam era M16 with similar punch at short range. In 2023, it will begin fielding a new slightly larger rifle which fires heavier caliber rounds farther, faster and more accurately in the same kind of close-quarters combat scenarios it initially acquired the M4 for.

New Hampshire-based arms manufacturer SIG Sauer was selected as the winner of the Army’s Next Generation Squad Weapon (NGSW) program early this year. Its SIG MCX-SPEAR rifle beat a trio of competitors to the $4.7 billion NGSW contract awarded in tandem with a $2.7 billion NGSW-Fire Control contract which went to a team including Vortex Optics and Sheltered Wings.

The rifle and a Squad Automatic Weapon (SGW) light machine gun variant (referred to as the M250) will be issued to as yet unannounced operational units early next year. The Army describes these as part of the “close combat force” which includes infantry, scouts and combat engineers. With the new weapon they’ll experience two significant changes.

The M5 carbine will fire 6.8 mm rounds as compared with the lighter 5.56 mm ammunition fired by the M4 and M249 (light machine gun). The NGSW System also marks the beginning of an era where combat weapons are coupled with a suppressor as standard issue equipment. The M5/M250 will use SIG Sauer SLX Suppressors (prominent at the gun muzzle) designed to reduce harmful gas backflow, sound signature and flash.

Few weapons systems are more intimate, more personal than a soldier’s issued rifle and the Army’s choice (the Marine Corps and Special Operations Command were included in the two-plus year testing and experimentation phase and have the option to adopt the M5) is significant, Mark Cancian, an adviser for the Center for Strategic Studies’ (CSIS) International Security Program, says.

“Going to a whole new caliber [round] is really quite significant. The last time the Army did this was in the 1960s when it went from the 7.62 mm [M14 rifle] to the 5.56 mm [M16].”

Cancian, who fired both the M14 and M16 in his Marine Corps career, adds that standardizing both the carbine and the SGW on the 6.8 mm caliber common-cartridge is important as well. That importance is presently underlined as the U.S. struggles to scale up munitions production of all kinds in reaction to the conflict in Ukraine and competitive pressure from the Chinese military in the Indo-Pacific.

In a DoD release on the weapons’ selection last April, Army Brigadier General Larry Q. Burris, the NGSW Soldier Lethality Cross-Functional Team director, emphasized that fielding the M5/M250 is “based upon ammunition production … As the vendor is able to produce ammunition and then Lake City [Army Ammuniton Plant in Missouri] ultimately comes on, what we don’t want to do is field a capability to a unit where we don’t have training ammunition or contingency ammunition, if required.”

The new 6.8 mm ammunition will initially be produced by SIG Sauer but the Army will eventually take over production of ammunition at Lake City around the 2025-2026 time frame. SIG Sauer will subsequently become a second-source provider of the new caliber. With ammunition production dictating the pace of the M5 rollout, the Army has said that the rest of the force will continue to carry the M4 and M249 for the coming decade or longer.

Cancian points out that the M5 will also demand a new stock of spare parts and training for armorers. “It’s going to be tricky. If you go slow in producing it, you’re going to have an Army with two different kinds of small arms for a decade.”

In a way, there is precedent. While the M4/M249 was introduced to the Army in the mid-1990s, it did not become the standard-issue Army rifle until 2010, ultimately replacing the M16. Close combat units received the M16 before the bulk of the Army when it was introduced in 1964 and as it went to war in Vietnam. However, it largely spread throughout the force in about five years’ time.

Today’s Army leaders would probably like that given the M5’s sophisticated fire control system, a computer-assisted optical display which provides aim correction, a ballistics computer and laser range finder. In a nod the soon-to-be-fielded, helmet-mounted Integrated Visual Augmentation System (IVAS), it also links wirelessly with future soldier electronics.

“The capability increase that these weapons provide over the M4 and the M249 is what’s really exciting,” project manager for soldier lethality, Army Col. Scott Madore, said in the Service’s release.

“The way it fires, the way, when you apply the fire control — it improves or increases the probability of a [hit] for the individual soldier. It reduces aim error, and it’s a game changer. That’s really what excites me about these two systems as we saw them go through testing.”

The Army says the M5 weighs about two pounds more than the M4 and, with similar dimensions, preserves the agility of the legacy rifle. In his book The M4 Carbine, author Chris McNab reminds us that Army interest in the M4 was spurred by the Battle of Mogadishu in 1993 in which Army Rangers complained that their M16 rifles were ‘unwieldy’. Delta Force troops in the same battle, equipped with the CAR-15 (a short-barreled commando version of the M16 made by Colt), had no such complaints.

Cancian admits he’s personally skeptical as to whether the M5 will be a game-changer. “People have very strong opinions about small arms. Is it better to have a lighter round weapon like the 5.56 mm [M4] that isn’t as lethal but is an easy weapon to use so you’re more likely to hit the target? Or is it better to have a heavier, more lethal round that’s more difficult to hit the target with? I fall in the former category.”

But with the minimal difference in weight between the old and new rifles and the fire control-assisted aim and augmentation, Cancian adds he’s open-minded about the M5/M250. The Army’s early experiences with the new SIG Sauer will be watched closely by the Marines and SOCOM. While Cancian believes there’s a strong chance the USMCUSMC
will adopt the M5 for logistical reasons if no other, he thinks SOCOM is more of a wild card. “They’ll do whatever is necessary to be different,” he says humorously.

Time, and some well-placed combat exposure, will tell if the new rifle/SAW/fire control system combination works as well as the Army expects. If it’s truly of a different caliber, the Service may opt for more than the up to 250,000 copies it says it may need.